Method for forming trench isolation using a gas cluster ion beam growth process

ABSTRACT

A method of forming shallow trench isolation on a substrate using a gas cluster ion beam (GCIB) is described. The method comprises generating a GCIB, and irradiating the substrate with the GCIB to form a shallow trench isolation structure by growing a dielectric layer in at least one region on the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 12/145,199, entitled METHOD FOR FORMING TRENCH ISOLATION, filed onJun. 24, 2008. The entire content of this application is hereinincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a method for forming a dielectric layer using agas cluster ion beam (GCIB), and more particularly to a method forforming a dielectric layer using a GCIB growth process.

2. Description of Related Art

Implementing electronic circuits involves connecting isolated devices orcircuit components through specific electronic paths. In silicon-basedintegrated circuit (IC) fabrication, it is necessary to isolate devicesthat are formed in a single substrate from one another. The individualdevices or circuit components subsequently are interconnected to createa specific circuit configuration.

As the density of the devices continues to rise, parasitic inter-devicecurrents become more problematic. Isolation technology, therefore, hasbecome an important aspect of IC fabrication. For example, dynamicrandom access memory (DRAM) devices generally comprise an array ofmemory cells for storing data and peripheral circuits for controllingdata in the memory cells. Each memory cell in a DRAM stores one bit ofdata and consists of one transistor and one capacitor. Within the array,each memory cell must be electrically isolated from adjacent memorycells. The degree to which large numbers of memory cells can beintegrated into a single IC chip depends, among other things, on thedegree of isolation between the memory cells. Similarly, inmetal-oxide-semiconductor (MOS) technology, isolation must be providedbetween adjacent devices, such as NMOS or PMOS transistors or CMOScircuits, to prevent parasitic channel formation.

Shallow trench isolation (STI) is one technique that can be used toisolate devices such as memory cells or transistors from one another.The typical STI process consists of a blanket pad oxide, and a blanketsilicon nitride followed by a trench mask and etch through the siliconnitride and pad oxide, and into the underlying crystalline siliconsubstrate. The mask is stripped and a liner oxide is grown and annealed.Next, high density plasma (HDP) oxide is deposited to fill the trenchand again heated to Denny the deposited oxide. Finally, the HDP oxideoverburden is polished back to the buried silicon nitride and thesilicon nitride/pad oxide is stripped prior to gate oxidation. As theHDP fills the trench it forms a vertical seam where the deposited layersof the HDP begin to join to fill the trench.

During the high temperature processing at liner oxide anneal and HDPoxide densification, stresses can develop because of non-uniform heatingof the substrate. Within the active region, these stresses can modifythe transistor performance. At the substrate level, non-uniformity ofstress can cause localized overlay registration errors during the gatemasking process. In addition, during the mechanical planarization, thisseam of the HDP is more vulnerable to over-etching as compared to theadjacent HDP layer. As a result, a defect can be created at the seamthat can lead to operational problems for the device.

Accordingly, it is desirable to improve the trench isolation techniquesto address those and similar problems.

SUMMARY OF THE INVENTION

The invention relates to a method for forming a dielectric layer using agas cluster ion beam (GCIB), and more particularly to a method forforming a dielectric layer using a GCIB growth process.

The invention further relates to a method for forming a dielectric layerfor trench isolation on a substrate using a GCIB.

According to one embodiment, a method of forming shallow trenchisolation on a substrate is described. The method comprises: generatinga GCIB; and irradiating the substrate with the GCIB to form a shallowtrench isolation (STI) structure by growing a dielectric layer in atleast one region on the substrate.

According to another embodiment, an integrated circuit is described. Theintegrated circuit comprises: a semiconductor substrate including afirst region; a plurality of active regions in the first region; and anSTI structure separating at least two of the active regions, wherein theSTI structure includes a dielectric trench having a dielectric linerformed by growing the dielectric liner on the semiconductor substrateusing a GCIB.

According to another embodiment, an STI structure of a semiconductorstructure is described. The STI structure contains a dielectric materialhaving a seam therein, wherein the dielectric material adjacent the seamis densified with one or more species introduced into an upper surfaceof the dielectric material using a GCIB.

According to another embodiment, a memory device is described. Thememory device comprises: a semiconductor substrate including a firstregion; a plurality of active regions provided in the first region; anSTI structure separating at least two of the active regions, wherein theSTI structure includes a dielectric trench having a dielectric linerformed by growing the dielectric liner on the semiconductor substrateusing a GCIB; and one or more species introduced into a surface of thedielectric trench using another GCIB, wherein the one or more speciesextend into the dielectric trench to a depth ranging from about 30 nm toabout 80 nm.

According to yet another embodiment, an electronic system is described.The electronic system comprises: a controller; and a memory devicecoupled to the controller, wherein the memory device comprises an arrayof memory cells. The memory cells comprise: a semiconductor substrateincluding a first region; a plurality of active regions in the firstregion; and an STI structure comprising a dielectric trench having adielectric liner that separates the active regions, wherein thedielectric liner is formed by growing the dielectric liner on thesemiconductor substrate using a GCIB, and wherein the dielectric trenchis densified with one or more species introduced into an upper surfaceof the dielectric trench using another GCIB.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A through 1D illustrate a cross-sectional view of an exemplaryportion of an STI structure according to an embodiment of the method;

FIGS. 2A through 2B illustrate a cross-sectional view of an exemplaryportion of an STI structure according to another embodiment of themethod;

FIGS. 3A through 3B illustrate a cross-sectional view of an exemplaryportion of an STI structure according to yet another embodiment of themethod;

FIG. 4 is a cross-sectional view of an exemplary integrated circuit thatincludes STI structures separating active regions according to anotherembodiment;

FIG. 5 is an illustration of a GCIB processing system;

FIG. 6 is another illustration of a GCIB processing system;

FIG. 7 is an illustration of an ionization source for a GCIB processingsystem; and

FIG. 8 is a flowchart illustrating a method of forming an STI structureon a substrate according to yet another embodiment.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

A method and system for preparing a dielectric layer on a substrateusing a gas cluster ion beam (GCIB) is disclosed in various embodiments.However, one skilled in the relevant art will recognize that the variousembodiments may be practiced without one or more of the specificdetails, or with other replacement and/or additional methods, materials,or components. In other instances, well-known structures, materials, oroperations are not shown or described in detail to avoid obscuringaspects of various embodiments of the invention. Similarly, for purposesof explanation, specific numbers, materials, and configurations are setforth in order to provide a thorough understanding of the invention.Nevertheless, the invention may be practiced without specific details.Furthermore, it is understood that the various embodiments shown in thefigures are illustrative representations and are not necessarily drawnto scale.

In the description and claims, the terms “coupled” and “connected,”along with their derivatives, are used. It should be understood thatthese terms are not intended as synonyms for each other. Rather, inparticular embodiments, “connected” may be used to indicate that two ormore elements are in direct physical or electrical contact with eachother while “coupled” may further mean that two or more elements are notin direct contact with each other, but yet still co-operate or interactwith each other.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, material, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention, but do not denote that theyare present in every embodiment. Thus, the appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily referring to the same embodimentof the invention. Furthermore, the particular features, structures,materials, or characteristics may be combined in any suitable manner inone or more embodiments. Various additional layers and/or structures maybe included and/or described features may be omitted in otherembodiments.

According to several embodiments, methods of forming shallow trenchisolation on a substrate are described. These methods include generatinga GCIB, and irradiating the substrate with the GCIB to form a shallowtrench isolation (STI) structure. A GCIB is generated and the GCIB isused to grow a dielectric layer in the substrate to a pre-determineddepth. One or more species may be introduced to the dielectric layer.Further, the dielectric material with the introduced species may bedensified through an annealing process.

A GCIB comprises gas clusters characterized by nano-sized aggregates ofmaterials that are gaseous under conditions of standard temperature andpressure. Such gas clusters may consist of aggregates including a few toseveral thousand molecules, or more, that are loosely bound together.The gas clusters can be ionized by electron bombardment, which permitsthe gas clusters to be formed into directed beams of controllableenergy. Such cluster ions each typically carry positive charges given bythe product of the magnitude of the electronic charge and an integergreater than or equal to one that represents the charge state of thecluster ion.

The larger sized cluster ions are often the most useful because of theirability to carry substantial energy per cluster ion, while yet havingonly modest energy per individual molecule. The ion clustersdisintegrate on impact with the substrate. Each individual molecule in aparticular disintegrated ion cluster carries only a small fraction ofthe total cluster energy. GCIBs can be formed by the condensation ofindividual gas atoms (or molecules) during the adiabatic expansion ofhigh pressure gas from a nozzle into a vacuum. A skimmer with a smallaperture strips divergent streams from the core of this expanding gasflow to produce a collimated beam of clusters. Neutral clusters ofvarious sizes are produced and held together by weak inter-atomic forcesknown as Van der Waals forces. Thereafter, gas clusters in the gascluster beam are ionized (e.g., by stripping one or more electrons) toform the GCIB.

“Substrate” or “substrate assembly” as used herein refers to asemiconductor substrate such as a base semiconductor layer or asemiconductor substrate having one or more layers, structures, orregions formed thereon. A base semiconductor layer is typically thelowest layer of silicon material on a wafer or a silicon layer depositedon another material, such as silicon on sapphire. When reference is madeto a substrate assembly, various process steps may have been previouslyused to form or define regions, junctions, various structures orfeatures, and openings such as capacitor plates or barriers forcapacitors.

“Layer” as used herein can refer to a layer formed on a substrate usinga deposition process. The term “layer” is meant to include layersspecific to the semiconductor industry, such as “barrier layer,”“dielectric layer,” and “conductive layer.” (The term “layer” issynonymous with the term “film” frequently used in the semiconductorindustry). The term “layer” is also meant to include layers found intechnology outside of semiconductor technology, such as coatings onglass.

Referring to FIG. 1A, a cross-sectional view of an exemplary portion ofan STI structure 1100 is shown according to an embodiment. The STIstructure 1100 includes a substrate 1102 that may be asilicon-containing structure or other semiconductor substrate thatincludes a bulk substrate region. For ease of illustration, the figuresshow active areas and STI field isolation regions in a single well type.However, in general, this and other embodiments are applicable to othersemiconductor device isolation regions such as n-well and p-well regionsin p-type substrates, n-type substrates and epitaxial substrates,including p on p+, p on p−, n on n+, and n on n− depending on the typeof semiconductor device being manufactured. In some implementations, thesubstrate 1102 can comprise gallium arsenide (GaAs) or othersemiconductor materials including, but not limited to: Si, Ge, SiGe,GaAs, InAs, InP, CdS, CdTe, other III/V compounds, and the like.

A layer of a pad oxide 1104, such as SiO₂, can be provided atop thesubstrate 1102, for example, either by deposition or by oxidizingprocess(es). In the latter, oxidation may include heating the substrate1102 in an oxygen ambient at high temperature (e.g., 800 degrees C. toabout 1100 degrees C.) until the oxide is formed on the surface of thesubstrate 1102. It is also possible to form pad oxide layer 1104 byconventional deposition processes such as, but not limited to: chemicalvapor deposition (CVD), plasma-enhanced CVD (PECVD), or physical vapordeposition (PVD). Further, it is possible to form pad oxide layer 1104using a GCIB to perform an oxidation process and grow the pad oxidelayer 1104.

A stop layer 1106, such as a nitride (e.g., SiN_(x)) layer, a carbide(e.g., SiC_(x)) layer, an oxynitride (e.g., SiO_(x)N_(y)) layer, acarbonitride (e.g., SiC_(x)N_(y)) layer, or other dielectric layer,which resists erosion during subsequent planarization and etching, isprovided over the pad oxide layer 1104 and defines an outer surface1108. A mask 1110, such as a layer of photoresist, then is deposited andpatterned as shown. The mask 1110 can be patterned by conventionalphotolithographic techniques. Other materials and additional layers mayalso be used to form the mask 1110 without departing from these andother embodiments.

Mask 1110 is patterned to expose regions for forming a trench 1112. Bytrench, it is meant to include any recessed contour, such as a hole,groove, and the like. Moreover, by substrate, it is meant to include anysemiconductor layer, and by substrate assembly, it is meant to includeany substrate having one or more layers formed thereon or doped regionsformed therein.

The stop layer 1106 and the pad oxide layer 1104 exposed through themask 1110 can then be removed. Suitable techniques for patterning theselayers include, but are not limited to, dry etching techniques and wetetching techniques. Dry etching techniques may include dry etching, wetetching, dry plasma etching, ion beam etching, GCIB etching, etc. Theetching process, indicated by the arrow, may continue through theselayers to remove at least a portion of the substrate 1102 in forming thetrench 1112. The depth that etching is performed into the substrate 1102to form the trench 1112 is typically from about 10 nm (nanometers) toabout 1000 nm. As will be appreciated, however, other depths may berequired depending upon the desired aspect ratio (i.e., depth to width)of the opening into the substrate 1102. An anisotropic etch such as aplasma or reactive ion etch (RIE) process can be used as the dry etchingprocess. The mask 1110 may then be removed by wet or dry stripping ofthe photoresist using conventional techniques, either before growing thedielectric layer, or thereafter as shown below.

Referring to FIG. 1B, a cross-sectional view of an exemplary portion ofthe STI structure 1100 depicted in FIG. 1A is shown during a step ofgrowing a dielectric layer 1114 at the base of trench 1112. A GCIB 1101is generated, and the substrate 1102, or one or more layers on thesubstrate 1102, is irradiated with the GCIB 1101 to form dielectriclayer 1114. The GCIB 1101 is used to grow dielectric layer 1114 in atleast one region on the substrate 1102 to a pre-determined depth. Thedielectric layer 1114 may include a bottom portion 1114A formed on abottom 1112A of trench 1112, and may optionally include a sidewallportion 1114B formed on sidewalls 1112B of trench 1112. The dielectriclayer 1114 may serve as a dielectric liner in trench 1112. Thedielectric layer 1114 may comprise an oxide, such as SiO₂ or moregenerally SiO_(x). Alternatively, the dielectric layer 1114 may comprisea nitride, such as SiN_(x) or the dielectric layer 1114 may comprise anoxynitride, such as SiO_(x)N_(y). When the substrate 1102, or theirradiated layer or layers on substrate 1102, comprises silicon, SiO₂,SiN_(x), or SiO_(x)N_(y) may be grown via the GCIB 1101 by using anoxygen-containing gas and/or nitrogen-containing gas, such as O₂, N₂,N₂O, NO₂, or NO. Furthermore, other materials may be introduced as well,e.g., carbon may be introduced to form a carbide using acarbon-containing gas, such as CH₄. Additional details for growing athin film or layer, using, for example, an oxidation process, areprovided in co-pending U.S. patent application Ser. No. 12/144,968,entitled METHOD AND SYSTEM FOR GROWING A THIN FILM USING A GAS CLUSTERION BEAM. The entire content of this application is herein incorporatedby reference in its entirety.

The GCIB 1101 may be formed using a GCIB processing system as discussedbelow.

The GCIB 1101 may be formed and accelerated by an acceleration potentialranging from about 1 kV to about 70 kV. Alternatively, the accelerationpotential may range from about 1 kV to about 20 kV. In one embodiment,the acceleration potential is selected based upon the desired depth forthe dielectric layer 1114. Alternatively, or in addition, the selectionof the acceleration potential may be made based upon the type oflayer(s) adjacent the dielectric layer 1114. A beam accelerationpotential and a beam dose are selected to achieve a thickness of thethin film ranging up to about 300 angstroms and to achieve a surfaceroughness of an upper surface of the thin film that is less than about20 angstroms. The GCIB is accelerated according to the beam accelerationpotential, and the accelerated GCIB is irradiated onto at least aportion of the substrate according to the beam dose. By doing so, thethin film is grown on the irradiated portion of the substrate to achievethe thickness and the surface roughness. For example, when growing aSiO₂ thin film, a beam acceleration potential of about 10 kV and a beamdose of about 2×10¹⁴ clusters per cm² can achieve a film thickness ofabout 140 angstroms and a surface roughness of about 8 angstroms orless. In one embodiment, the beam energy distribution function for theGCIB is modified to change said thickness of said thin film, or saidsurface roughness of said thin film, or both. As an example, one maybroaden the beam energy distribution to decrease the surface roughnessof the thin film, or one may narrow the beam energy distribution toincrease the surface roughness of the thin film.

Additionally, as shown in FIG. 1B, the formation of dielectric layer1114 in trench 1112 may be directional. For example, material growth mayproceed on one or more surfaces that are substantially perpendicular tothe incident GCIB while material growth may be substantially avoided orreduced on one or more surfaces that are substantially parallel with theincident GCIB. However, the directionality of the film growth may beadjusted such that some growth occurs on one or more surfaces that aresubstantially parallel with the incident GCIB, e.g., the sidewalls 1112Bof trench 1112.

For example, as the GCIB energy (or beam acceleration potential) isincreased or decreased, the anisotropy (or directionality) of the GCIBmay be increased or decreased, respectively. Therefore, by adjusting thebeam acceleration potential, an amount of the thin film grown ordeposited on the sidewalls 1112B of trench 1112 relative to the bottom1112A of trench 1112 may be varied. Alternatively, for example,adjusting the orientation of the substrate relative to the direction ofincidence of the GCIB may permit growth to proceed on other surfaces.Alternatively yet, adjusting the GCIB energy distribution (i.e.,broadening or narrowing) may permit growth to proceed on other surfaces.

Moreover, one or more properties of the GCIB, including the beamcomposition, can be adjusted or alternated in order to directionallygrade the growth of multi-layer material films having differingproperties from one sub-layer to an adjacent sub-layer on one or moresurfaces substantially perpendicular to the incident GCIB.

Referring to FIG. 1C, a cross-sectional view of an exemplary portion ofthe STI structure depicted in FIG. 1B is shown after at least partiallyfilling trench 1112 with a second dielectric layer 1116. Seconddielectric layer 1116 may be formed of a doped or un-doped silicon oxide(e.g., SiO₂). Some un-doped silicon oxides include thermal TEOS(tetraethyl orthosilicate) and high-density plasma (HDP) silicon oxides.Some doped silicon oxides include PSG (phosphosilicate glass), BSG(borosilicate glass), BPSG (borophosphosilicate glass), B-TEOS(boron-doped TEOS), P-TEOS (phosphorous-doped TEOS), F-TEOS (fluorinatedTEOS), silicon germanium oxide, and the like. For example, PECVD may beused to deposit the dielectric material to fill trench 1112 and formsecond dielectric layer 1116.

Referring to FIG. 1D, the STI structure 1100 depicted in FIG. 1C may besubjected to various planarization techniques to planarize the seconddielectric layer 1116 down to the stop layer 1106. The planarizationtechnique may include a mechanical planarization technique, such aschemical-mechanical planarization (CMP), or ion beam etching, such asGCIB planarizing or etching.

Referring still to FIG. 1D, the STI structure 1100 is irradiated by asecond GCIB 1126 to introduce one or more species in an upper portion1128 of the second dielectric layer 1116. As used herein, an upperportion 1128 of the second dielectric layer 1116 includes an exposedsurface 1130 along with a pre-determined depth 1132 of the dielectricmaterial extending into the second dielectric layer 1116. As usedherein, the one or more species that are introduced into the upperportion 1128 are delivered to the exposed surface 1130 via second GCIB1126 in the form of energetic gas cluster ions. These gas cluster ionsare formed, as described above, via the expansion of a high pressure gasinto a vacuum and the subsequent (electron impact) ionization of theresulting gas clusters.

According to one embodiment, the pre-determined depth 1132 may rangefrom about 30 nm to about 80 nm. Alternatively, or in addition, the oneor more species may be introduced or infused at the surface 1130 of thesecond dielectric layer 1116 to a depth at least as great as the depthof the stop layer 1106 and the pad oxide 1104. More generally, thepre-determined depth 1132 of the introduced species that are infusedinto the second dielectric layer 1116 may be in the range of about 3% toabout 80% the depth of the trench 1112. In one example, the introducedspecies are infused to a depth in the range of about 10% to about 40%the depth of the trench 1112. The introduced species infused in theupper portion 1128 of the second dielectric layer 1116 may also have agradation of species concentration that decreases as the distance fromthe surface 1130 into the trench 1112 increases.

Examples of suitable feed gas that may be introduced to produce the GCIBinclude one or more gaseous species containing O₂, N₂, Xe, Ar, Si, BF₂,or Ge, or any combination of two or more thereof. Additionally, examplesof suitable feed gas that may be introduced to produce the GCIB includeone or more gaseous species containing O, N, C, H, S, Si, Ge, F, Cl, Br,He, Ne, Xe, Ar, B, P, or As, or any combination of two or more thereof.The resultant flux of the species at the surface can be expressed as adensity of atoms (or molecules) per area (e.g., atoms/cm²) for a givenexposure time.

The second GCIB 1126 may be formed using a GCIB processing system asdiscussed below. The second GCIB 1126 may be formed and accelerated byan acceleration potential ranging from about 1 kV to about 70 kV.Alternatively, the acceleration potential may range from about 1 kV toabout 20 kV. In one embodiment, the acceleration potential is selectedbased upon the desired depth of the introduced species infused into thesecond dielectric layer 1116. Alternatively, or in addition, theselection of the acceleration potential may be made based upon the typeof layer(s) adjacent the second dielectric layer 1116.

Densification of the one or more species introduced to second dielectriclayer 1116 may be performed to reduce the high wet removal (e.g., etch)rate and/or seam propagation of the second dielectric layer 1116 duringpost mechanical planarization wet clean processing. The densificationprocess may be used in conjunction with standard substantiallynon-oxidizing anneals, and applied after the mechanical planarizationcleaning step. The resulting densification may provide enough wet etchmargin against STI fill recess and keyhole propagation during subsequentprocessing steps. In addition, the densification of the introducedspecies infused into second dielectric layer 1116 may be obtained atlower temperatures and less corrosive oxidizing ambient without overlyreacting with the substrate materials.

The STI structure 1100 of FIG. 1D may be annealed under conditionseffective to Denny the one or more species infused into the seconddielectric layer 1116. Specifically, the annealing conditions employedmay be selected so that the removal rate of the annealed species infusedinto second dielectric layer 1116 substantially matches that of theadjacent stop layer 1106. This selective annealing step may ensure thatany subsequent removal process (e.g., etching) will remove the energeticspecies infused into second dielectric layer 1116 and the stop layer1106 at similar rates thus preventing the formation of any isotropicdefects or “divots” in the second dielectric layer 1116.

In one embodiment, annealing may be carried out in an inert gasatmosphere, e.g., nitrogen, argon, helium and the like, which may or maynot be mixed with O₂, N₂O, NO₂, or NO. One example of an atmosphereemployed in the annealing step is steam at a temperature of about 600degrees C. to about 700 degrees C. for a time interval ranging fromabout 30 seconds to about 120 seconds. In an additional example, theatmosphere employed for the annealing step is steam at a temperaturefrom about 75 degrees C. to about 600 degrees C. for a time intervalranging from about 30 seconds to about 120 seconds. It should be notedthat the annealing step may be carried out in a single ramp step or itcan be carried out using a series of ramp and soak cycles.

After annealing and densification of the one or more species introducedinto second dielectric layer 1116, the STI structure 1100 may besubjected to a selective removal step which is highly selective inremoving the stop layer 1106. Suitable oxide etching techniques that maybe employed include, but are not limited to, wet etching techniquesand/or dry etching techniques, such as reactive ion etching (RIE),plasma etching, ion beam etching, GCIB etching, and chemical dryetching. The gases that may be employed in these etching techniques arethose that have a high affinity and selectivity for the stop layer 1106,as well as the one or more species introduced into second dielectriclayer 1116.

For dry etching processes, examples of suitable gases that can beemployed in the dry etching process include: CF₄, SF₆, NF₃, CHF₃, CH₂F₂,C₄F₆, C₄F₈, C₅F₈, HBr, Cl₂, Br₂, BCl₃, and combinations thereof. Thegases may also be used in conjunction with oxygen-containing gas,carbon-containing gas, hydrogen-containing gas, nitrogen-containing gas,or an inert gas such as a noble gas. For wet etching processes, suitablechemical etchants may include, but not be limited to, HF and/or HNO₃.

Referring now to FIG. 2A, a cross-sectional view of an exemplary portionof an STI structure 1200 is shown according to another embodiment. TheSTI structure 1200 includes a substrate 1202 that may be asilicon-containing structure or other semiconductor substrate thatincludes a bulk substrate region. For ease of illustration, the figuresshow active areas and STI field isolation regions in a single well type.However, in general, this and other embodiments are applicable to othersemiconductor device isolation regions such as n-well and p-well regionsin p-type substrates, n-type substrates and epitaxial substrates,including p on p+, p on p−, n on n+, and n on n− depending on the typeof semiconductor device being manufactured. In some implementations, thesubstrate 1202 can comprise gallium arsenide (GaAs) or othersemiconductor materials including, but not limited to: Si, Ge, SiGe,GaAs, InAs, InP, CdS, CdTe, other III/V compounds, and the like.

Referring to FIG. 2B, a cross-sectional view of an exemplary portion ofthe STI structure 1200 depicted in FIG. 2A is shown during a step ofgrowing a dielectric layer 1204. A GCIB 1201 is generated, and thesubstrate 1202, or one or more layers on the substrate 1202, isirradiated with the GCIB 1201 to form dielectric layer 1204. The GCIB1201 is used to grow dielectric layer 1204 in at least one region on thesubstrate 1202 to a pre-determined depth. The dielectric layer 1204comprises a first region 1211 having a shallow penetration depth thatmay serve as a pad oxide layer, and the dielectric layer 1204 comprisesa second region 1212 having a relatively deeper penetration depth thatmay serve as trench isolation. Alternatively, the dielectric layer 1204is grown in the second region 1212 and is not grown in the first region1211.

The dielectric layer 1204 may comprise an oxide, such as SiO₂ or moregenerally SiO_(x). Alternatively, the dielectric layer 1204 may comprisea nitride, such as SiN_(x) or the dielectric layer 1204 may comprise anoxynitride, such as SiO_(x)N_(y). When the substrate 1202, or theirradiated layer or layers on substrate 1202, comprises silicon, SiO₂,SiN_(x), or SiO_(x)N_(y) may be grown via a GCIB generated using anoxygen-containing gas and/or a nitrogen-containing gas, such as O₂, N₂,N₂O, NO₂, or NO. Additional details for growing a thin film or layer,using, for example, an oxidation process, are provided in co-pendingU.S. patent application Ser. No. 12/144,968, entitled METHOD AND SYSTEMFOR GROWING A THIN FILM USING A GAS CLUSTER ION BEAM, the entire contentof which is herein incorporated by reference in its entirety.

According to one embodiment, the variation of the penetration depthbetween the first region 1211 and the second region 1212 is achieved byvarying the GCIB dose (e.g., time and/or beam current) or the GCIBenergy (e.g., GCIB acceleration potential), or both. According toanother embodiment, this variation in penetration depth may be achievedby forming one or more mask layers (not shown) on substrate 1202 havinga pattern created therein that is approximately aligned with the secondregion 1212, exposing the substrate 1202 to a first GCIB oxidationprocess configured to produce a relatively deeper penetration depth forthe grown dielectric layer in the second region 1212, removing the oneor more mask layers, and exposing the substrate 1202 to a second GCIBoxidation process configured to produce a relatively shallowerpenetration depth for the grown dielectric layer in the first region1211.

The GCIB 1201 may be formed using a GCIB processing system as discussedbelow. The GCIB 1201 may be formed and accelerated by an accelerationpotential ranging from about 1 kV to about 70 kV. Alternatively, theacceleration potential may range from about 1 kV to about 20 kV. In oneembodiment, the acceleration potential is selected based upon thedesired depth for the dielectric layer 1204. Alternatively, or inaddition, the selection of the acceleration potential may be made basedupon the type of layer(s) adjacent the dielectric layer 1204.

Dielectric layer 1204 may be modified by infusing one or more atomic ormolecular species, by densification, or by annealing, or any combinationof two or more thereof.

Referring to FIG. 3A, a cross-sectional view of an exemplary portion ofan STI structure 1300 is shown according to an embodiment. The STIstructure 1300 includes a substrate 1302 that may be asilicon-containing structure or other semiconductor substrate thatincludes a bulk substrate region. For ease of illustration, the figuresshow active areas and STI field isolation regions in a single well type.However, in general, this and other embodiments are applicable to othersemiconductor device isolation regions such as n-well and p-well regionsin p-type substrates, n-type substrates and epitaxial substrates,including p on p+, p on p−, n on n+, and n on n− depending on the typeof semiconductor device being manufactured. In some implementations, thesubstrate 1302 can comprise gallium arsenide (GaAs) or othersemiconductor materials including, but not limited to: Si, Ge, SiGe,GaAs, InAs, InP, CdS, CdTe, other III/V compounds, and the like.

A layer of a pad oxide 1304, such as SiO₂, can be provided atop thesubstrate 1302, for example, either by deposition or by oxidizingprocess(es). In the latter, oxidation may include heating the substrate1302 in an oxygen ambient at high temperature (e.g., 800 degrees C. toabout 1100 degrees C.) until the oxide is formed on the surface of thesubstrate 1302. It is also possible to form pad oxide layer 1304 byconventional deposition processes such as, but not limited to: chemicalvapor deposition (CVD), plasma-enhanced CVD (PECVD), or physical vapordeposition (PVD). Further, it is possible to form pad oxide layer 1304using a GCIB to perform an oxidation process and grow the pad oxidelayer 1304.

An optional stop layer 1306, such as a nitride (e.g., SiN_(x)) layer, acarbide (e.g., SiC_(x)) layer, an oxynitride (e.g., SiO_(x)N_(y)) layer,a carbonitride (e.g., SiC_(x)N_(y)) layer, or other dielectric layer,which resists erosion during subsequent planarization and etching, maybe provided over the pad oxide layer 1304 and may define an outersurface 1308. A mask 1310, such as a layer of photoresist, then isdeposited and patterned as shown. The mask 1310 can be patterned byconventional photolithographic techniques. Other materials andadditional layers may also be used to form the mask 1310 withoutdeparting from these and other embodiments.

Mask 1310 is patterned to expose regions for growing a dielectric layer1312 in substrate 1302. By substrate, it is meant to include anysemiconductor layer, and by substrate assembly, it is meant to includeany substrate having one or more layers formed thereon or doped regionsformed therein.

The stop layer 1306 and the pad oxide layer 1304 exposed through themask 1310 can then be removed. Suitable techniques for patterning theselayers include, but are not limited to, dry etching techniques and wetetching techniques. Dry etching techniques may include dry etching, wetetching, dry plasma etching, ion beam etching, GCIB etching, etc. Themask 1310 may then be removed by wet or dry stripping of the photoresistusing conventional techniques.

Referring to FIG. 3B, a cross-sectional view of an exemplary portion ofthe STI structure 1300 depicted in FIG. 3A is shown during a step ofgrowing a dielectric layer 1312. A GCIB 1301 is generated, and thesubstrate 1302, or one or more layers on the substrate 1302, isirradiated with the GCIB 1301 to form dielectric layer 1312. The GCIB1301 is used to grow dielectric layer 1312 in at least one region on thesubstrate 1302 to a pre-determined depth. The dielectric layer 1312 maycomprise an oxide, such as SiO₂. Alternatively, the dielectric layer1312 may comprise a nitride, such as SiN_(x) or the dielectric layer1312 may comprise an oxynitride, such as SiO_(x)N_(y). When thesubstrate 1302, or the irradiated layer or layers on substrate 1302,comprises silicon, SiO₂ may be grown via GCIB 1301 using anoxygen-containing gas, such as O₂. Additional details for growing a thinfilm or layer, using, for example, an oxidation process, are provided inco-pending U.S. patent application Ser. No. 12/144,968, entitled METHODAND SYSTEM FOR GROWING A THIN FILM USING A GAS CLUSTER ION BEAM, theentire content of which is herein incorporated by reference in itsentirety.

The GCIB 1301 may be formed using a GCIB processing system as discussedbelow. The GCIB 1301 may be formed and accelerated by an accelerationpotential ranging from about 1 kV to about 70 kV. Alternatively, theacceleration potential may range from about 1 kV to about 20 kV. In oneembodiment, the acceleration potential is selected based upon thedesired depth for the dielectric layer 1312. Alternatively, or inaddition, the selection of the acceleration potential may be made basedupon the type of layer(s) adjacent the dielectric layer 1312.

Dielectric layer 1312 may be modified by infusing one or more atomic ormolecular species, by densification, or by annealing, or any combinationof two or more thereof.

Additional processes can be performed using known techniques to completean integrated circuit (IC) for use in an electronic system that includesa controller (e.g., a processor) and active semiconductor regionsseparated by the STI structure, wherein the STI structure includes adielectric trench having a dielectric liner formed by growing thedielectric liner on the semiconductor substrate using a GCIB. Varioustypes of devices may be formed in the active areas. Such devices includeimaging devices, memory devices or logic devices. For example, thecompleted IC may include an array of memory cells for a DRAM or othermemory device. In other ICs, logic devices for gate arrays,microprocessors or digital signal processors may be formed in the activeregions. The STI structure 1100, 1200, 1300 may separate the activeregions from one another.

Other embodiments further include an integrated circuit, methods offorming the integrated circuit, memory devices, and electronic systemsthat include the memory devices, having a plurality of active regions ina first region of a semiconductor substrate that are separated by STIstructures. As discussed herein, dielectric trenches separating at leasttwo of the active regions from one another may include dielectric linersformed by growing the dielectric liners on the semiconductor substrateusing a GCIB.

As discussed herein, one or more species are then directed at an uppersurface of the substrate using a GCIB after at least partially fillingthe trenches with the dielectric material. In one embodiment, ionizedgas clusters containing the one or more species are infused at a depthof about 30 nm to about 80 nm below the surface of the dielectricmaterial. The dielectric material filling the trench may also include aseam, as discussed herein. Upon densification, the one or more speciesinfused into a surface of the dielectric material may provide foruniform wet etch rates across the surface of the dielectric material,including the seam. FIG. 4 illustrates portions of exemplary integratedcircuits that include STI structures separating active regions. The STIstructures may be formed using the techniques described above.

In FIG. 4, a stacked-cell DRAM 1440 includes a semiconductor substrate1442 with multiple active regions 1444A, 1444B, 1444C separated by STIregions 1446A, 1446B. Each isolation region 1446A, 1446B includes thedielectric layer formed according to embodiments described above.

Impurity-doped regions 1452, 1453 may be formed, for example, by adiffusion implanted or infused process with the regions 1452 serving asstorage nodes (e.g., source and drain) for memory cells of the DRAM andthe regions 1453 serving as contact nodes. Stacked gates are providedover the gate oxide layers 1456 with nitride or other spacers 1458provided on either side of the gates. The stacked gates include apolysilicon layer 1454 and an insulating layer 1455. The insulatinglayer 1455 may include, for example, a deposited oxide, a depositednitride, or a composite stack of oxide/nitride or oxide/nitride/oxidelayers. In some implementations, each gate stack also includes asilicide layer between the polysilicon layer 1454 and the insulatinglayer 1455. The silicide layer may include, for example, a tungstensilicide, a titanium silicide or a cobalt silicide. In yet otherimplementations, the gate stack includes a barrier metal layer and ametal layer between the polysilicon layer 1454 and the insulating layer1455. Suitable barrier metal layers include tungsten nitride, titaniumnitride and tantalum nitride. The metal layer may include tungsten,tungsten silicide, titanium silicide, or cobalt silicide. Polysiliconplugs 1460 form the contacts to the regions 1452.

In the illustrated IC of FIG. 4, capacitor cells comprise lower storagenode electrodes 1462, a cell dielectric 1464 and an upper electrode1466. A metal contact 1468 provides the electrical connection betweenone of the polysilicon plugs 1460, which serves as the bit line, and afirst metallization layer 1470. An insulating layer 1472 separates thefirst metallization layer 1470 from a second metallization layer 1474.The entire semiconductor wafer is covered by a passivation layer 1476.

Although FIG. 4 illustrates a stacked-cell DRAM, isolation regionsformed according to the techniques described above can be incorporatedinto any other type of memory such as trench cell DRAMs, flash memory,embedded memory, electrically erasable programmable read only memory(EEPROM), and the like.

As described above, one or more dielectric layers in one or more regionson a substrate may be grown by generating a GCIB in a GCIB processingsystem and irradiating the substrate with the GCIB. The GCIB may be usedto grow a dielectric film or grow a trench liner prior to depositing thedielectric material. For example, a GCIB containing O₂ may be used togrow SiO₂ on silicon. Additionally, a second GCIB may be used tointroduce one or more species to a dielectric material. Furthermore, athird GCIB may be used to planarize the deposited dielectric material.For example, a GCIB containing CF₄, NF₃, or SF₆ may be used to planarizethe dielectric material. Additionally yet, a fourth GCIB may be used toetch the dielectric material, the stop layer, or both the dielectricmaterial and the stop layer. For example, a GCIB containing CF₄, NF₃, orSF₆ may be used to etch the dielectric material or stop layer. Furtheryet, a fifth GCIB may be used to form the trench. For example, a GCIBcontaining NF₃ or SF₆ may be used to etch a trench or via in silicon.

According to an embodiment, a GCIB processing system 100 for, amongother things, generating the GCIB for growing a dielectric materiallayer is depicted in FIG. 5. The GCIB processing system 100 comprises avacuum vessel 102, substrate holder 150, upon which a substrate 152 tobe processed is affixed, and vacuum pumping systems 170A, 170B, and170C. Substrate 152 can be a semiconductor substrate, a wafer, a flatpanel display (FPD), a liquid crystal display (LCD), or any otherworkpiece. GCIB processing system 100 is configured to produce a GCIBfor treating substrate 152.

Referring still to GCIB processing system 100 in FIG. 5, the vacuumvessel 102 comprises three communicating chambers, namely, a sourcechamber 104, an ionization/acceleration chamber 106, and a processingchamber 108 to provide a reduced-pressure enclosure. The three chambersare evacuated to suitable operating pressures by vacuum pumping systems170A, 170B, and 170C, respectively. In the three communicating chambers104, 106, 108, a gas cluster beam can be formed in the first chamber(source chamber 104), while a GCIB can be formed in the second chamber(ionization/acceleration chamber 106) wherein the gas cluster beam isionized and optionally accelerated. Then in the third chamber(processing chamber 108), the accelerated or non-accelerated GCIB may beutilized to treat substrate 152.

As shown in FIG. 5, GCIB processing system 100 can comprise one or moregas sources configured to introduce one or more gases or mixture ofgases to vacuum vessel 102. For example, a first gas composition storedin a first gas source 111 is admitted under pressure through a first gascontrol valve 113A to a gas metering valve or valves 113. Additionally,for example, a second gas composition stored in a second gas source 112is admitted under pressure through a second gas control valve 113B tothe gas metering valve or valves 113. Furthermore, for example, thefirst gas composition or the second gas composition or both can comprisea gas composition containing one or more species for growing thedielectric material or for infusion into the dielectric material.Further yet, for example, the first gas composition or second gascomposition or both can include a condensable inert gas, carrier gas ordilution gas. For example, the inert gas, carrier gas or dilution gascan include a noble gas, i.e., He, Ne, Ar, Kr, Xe, or Rn. Furthermore,the first gas source 111 and the second gas source 112 may be utilizedeither alone or in combination with one another to produce ionizedclusters.

The high pressure, condensable gas comprising the first gas compositionor the second gas composition or both is introduced through gas feedtube 114 into stagnation chamber 116 and is ejected into thesubstantially lower pressure vacuum through a properly shaped nozzle110. As a result of the expansion of the high pressure, condensable gasfrom the stagnation chamber 116 to the lower pressure region of thesource chamber 104, the gas velocity accelerates to supersonic speedsand gas cluster beam 118 emanates from nozzle 110.

The inherent cooling of the jet as static enthalpy is exchanged forkinetic energy, which results from the expansion in the jet, causes aportion of the gas jet to condense and form a gas cluster beam 118having clusters, each consisting of from several to several thousandweakly bound atoms or molecules. A gas skimmer 120, positioneddownstream from the exit of the nozzle 110 between the source chamber104 and ionization/acceleration chamber 106, partially separates the gasmolecules on the peripheral edge of the gas cluster beam 118, that maynot have condensed into a cluster, from the gas molecules in the core ofthe gas cluster beam 118, that may have formed clusters. Among otherreasons, this selection of a portion of gas cluster beam 118 can lead toa reduction in the pressure in the downstream regions where higherpressures may be detrimental (e.g., ionizer 122, and processing chamber108). Furthermore, gas skimmer 120 defines an initial dimension for thegas cluster beam entering the ionization/acceleration chamber 106.

After the gas cluster beam 118 has been formed in the source chamber104, the constituent gas clusters in gas cluster beam 118 are ionized byionizer 122 to form GCIB 128. The ionizer 122 may include an electronimpact ionizer that produces electrons from one or more filaments 124,which are accelerated and directed to collide with the gas clusters inthe gas cluster beam 118 inside the ionization/acceleration chamber 106.Upon collisional impact with the gas cluster, electrons of sufficientenergy eject electrons from molecules in the gas clusters to generateionized molecules. The ionization of gas clusters can lead to apopulation of charged gas cluster ions, generally having a net positivecharge.

As shown in FIG. 5, beam electronics 130 are utilized to ionize,extract, accelerate, and focus the GCIB 128. The beam electronics 130include a filament power supply 136 that provides voltage V_(F) to heatthe ionizer filament 124.

Additionally, the beam electronics 130 include a set of suitably biasedhigh voltage electrodes 126 in the ionization/acceleration chamber 106that extracts the cluster ions from the ionizer 122. The high voltageelectrodes 126 then accelerate the extracted cluster ions to a desiredenergy and focus them to define GCIB 128. The kinetic energy of thecluster ions in GCIB 128 typically ranges from about 1000 electron volts(1 keV) to several tens of keV. For example, GCIB 128 can be acceleratedto 1 to 70 keV.

As illustrated in FIG. 5, the beam electronics 130 further include ananode power supply 134 that provides voltage V_(A) to an anode ofionizer 122 for accelerating electrons emitted from filament 124 andcausing the electrons to bombard the gas clusters in gas cluster beam118, which produces cluster ions.

Additionally, as illustrated in FIG. 5, the beam electronics 130 includean extraction power supply 138 that provides voltage V_(E) to bias atleast one of the high voltage electrodes 126 to extract ions from theionizing region of ionizer 122 and to form the GCIB 128. For example,extraction power supply 138 provides a voltage to a first electrode ofthe high voltage electrodes 126 that is less than or equal to the anodevoltage of ionizer 122.

Furthermore, the beam electronics 130 can include an accelerator powersupply 140 that provides voltage V_(Acc) to bias one of the high voltageelectrodes 126 with respect to the ionizer 122 so as to result in atotal GCIB acceleration energy equal to about V_(Acc) electron volts(eV). For example, accelerator power supply 140 provides a voltage to asecond electrode of the high voltage electrodes 126 that is less than orequal to the anode voltage of ionizer 122 and the extraction voltage ofthe first electrode.

Further yet, the beam electronics 130 can include lens power supplies142, 144 that may be provided to bias some of the high voltageelectrodes 126 with potentials (e.g., V_(L1) and V_(L2)) to focus theGCIB 128. For example, lens power supply 142 can provide a voltage to athird electrode of the high voltage electrodes 126 that is less than orequal to the anode voltage of ionizer 122, the extraction voltage of thefirst electrode, and the accelerator voltage of the second electrode,and lens power supply 144 can provide a voltage to a fourth electrode ofthe high voltage electrodes 126 that is less than or equal to the anodevoltage of ionizer 122, the extraction voltage of the first electrode,the accelerator voltage of the second electrode, and the first lensvoltage of the third electrode.

Note that many variants on both the ionization and extraction schemesmay be used. While the scheme described here is useful for purposes ofinstruction, another extraction scheme involves placing the ionizer andthe first element of the extraction electrode(s) (or extraction optics)at V_(Acc). This typically requires fiber optic programming of controlvoltages for the ionizer power supply, but creates a simpler overalloptics train. The invention described herein is useful regardless of thedetails of the ionizer and extraction lens biasing.

A beam filter 146 in the ionization/acceleration chamber 106 downstreamof the high voltage electrodes 126 can be utilized to eliminatemonomers, or monomers and light cluster ions from the GCIB 128 to definea filtered process GCIB 128A that enters the processing chamber 108. Inone embodiment, the beam filter 146 substantially reduces the number ofclusters having 100 or less atoms or molecules or both. The beam filtermay comprise a magnet assembly for imposing a magnetic field across theGCIB 128 to aid in the filtering process.

Referring still to FIG. 5, a beam gate 148 is disposed in the path ofGCIB 128 in the ionization/acceleration chamber 106. Beam gate 148 hasan open state in which the GCIB 128 is permitted to pass from theionization/acceleration chamber 106 to the processing chamber 108 todefine process GCIB 128A, and a closed state in which the GCIB 128 isblocked from entering the processing chamber 108. A control cableconducts control signals from control system 190 to beam gate 148. Thecontrol signals controllably switch beam gate 148 between the open orclosed states.

A substrate 152, which may be a wafer or semiconductor wafer, a flatpanel display (FPD), a liquid crystal display (LCD), or other substrateto be processed by GCIB processing, is disposed in the path of theprocess GCIB 128A in the processing chamber 108. Because mostapplications contemplate the processing of large substrates withspatially uniform results, a scanning system may be desirable touniformly scan the process GCIB 128A across large areas to producespatially homogeneous results.

An X-scan actuator 160 provides linear motion of the substrate holder150 in the direction of X-scan motion (into and out of the plane of thepaper). A Y-scan actuator 162 provides linear motion of the substrateholder 150 in the direction of Y-scan motion 164, which is typicallyorthogonal to the X-scan motion. The combination of X-scanning andY-scanning motions translates the substrate 152, held by the substrateholder 150, in a raster-like scanning motion through process GCIB 128Ato cause a uniform (or otherwise programmed) irradiation of a surface ofthe substrate 152 by the process GCIB 128A for processing of thesubstrate 152.

The substrate holder 150 disposes the substrate 152 at an angle withrespect to the axis of the process GCIB 128A so that the process GCIB128A has an angle of beam incidence 166 with respect to a substrate 152surface. The angle of beam incidence 166 may be 90 degrees or some otherangle, but is typically 90 degrees or near 90 degrees. DuringY-scanning, the substrate 152 and the substrate holder 150 move from theshown position to the alternate position “A” indicated by thedesignators 152A and 150A, respectively. Notice that in moving betweenthe two positions, the substrate 152 is scanned through the process GCIB128A, and in both extreme positions, is moved completely out of the pathof the process GCIB 128A (over-scanned). Though not shown explicitly inFIG. 1, similar scanning and over-scan is performed in the (typically)orthogonal X-scan motion direction (in and out of the plane of thepaper).

A beam current sensor 180 may be disposed beyond the substrate holder150 in the path of the process GCIB 128A so as to intercept a sample ofthe process GCIB 128A when the substrate holder 150 is scanned out ofthe path of the process GCIB 128A. The beam current sensor 180 istypically a faraday cup or the like, closed except for a beam-entryopening, and is typically affixed to the wall of the vacuum vessel 102with an electrically insulating mount 182.

As shown in FIG. 5, control system 190 connects to the X-scan actuator160 and the Y-scan actuator 162 through electrical cable and controlsthe X-scan actuator 160 and the Y-scan actuator 162 in order to placethe substrate 152 into or out of the process GCIB 128A and to scan thesubstrate 152 uniformly relative to the process GCIB 128A to achievedesired processing of the substrate 152 by the process GCIB 128A.Control system 190 receives the sampled beam current collected by thebeam current sensor 180 by way of an electrical cable and, thereby,monitors the GCIB and controls the GCIB dose received by the substrate152 by removing the substrate 152 from the process GCIB 128A when apre-determined dose has been delivered.

In the embodiment shown in FIG. 6, the GCIB processing system 200 can besimilar to the embodiment of FIG. 5 and further comprise a X-Ypositioning table 253 operable to hold and move a substrate 252 in twoaxes, effectively scanning the substrate 252 relative to the processGCIB 128A. For example, the X-motion can include motion into and out ofthe plane of the paper, and the Y-motion can include motion alongdirection 264.

The process GCIB 128A impacts the substrate 252 at a projected impactregion 286 on a surface of the substrate 252, and at an angle of beamincidence 266 with respect to the substrate 252 surface. By X-Y motion,the X-Y positioning table 253 can position each portion of a surface ofthe substrate 252 in the path of process GCIB 128A so that every regionof the surface may be made to coincide with the projected impact region286 for processing by the process GCIB 128A. An X-Y controller 262provides electrical signals to the X-Y positioning table 253 through anelectrical cable for controlling the position and velocity in each ofX-axis and Y-axis directions. The X-Y controller 262 receives controlsignals from, and is operable by, control system 190 through anelectrical cable. X-Y positioning table 253 moves by continuous motionor by stepwise motion according to conventional X-Y table positioningtechnology to position different regions of the substrate 252 within theprojected impact region 286. In one embodiment, X-Y positioning table253 is programmably operable by the control system 190 to scan, withprogrammable velocity, any portion of the substrate 252 through theprojected impact region 286 for GCIB processing by the process GCIB128A.

The substrate holding surface 254 of positioning table 253 iselectrically conductive and is connected to a dosimetry processoroperated by control system 190. An electrically insulating layer 255 ofpositioning table 253 isolates the substrate 252 and substrate holdingsurface 254 from the base portion 260 of the positioning table 253.Electrical charge induced in the substrate 252 by the impinging processGCIB 128A is conducted through substrate 252 and substrate holdingsurface 254, and a signal is coupled through the positioning table 253to control system 190 for dosimetry measurement. Dosimetry measurementhas integrating means for integrating the GCIB current to determine aGCIB processing dose. Under certain circumstances, a target-neutralizingsource (not shown) of electrons, sometimes referred to as electronflood, may be used to neutralize the process GCIB 128A. In such case, aFaraday cup (not shown, but which may be similar to beam current sensor180 in FIG. 5) may be used to assure accurate dosimetry despite theadded source of electrical charge the reason being that typical Faradaycups allow only the high energy positive ions to enter and be measured.

In operation, the control system 190 signals the opening of the beamgate 148 to irradiate the substrate 252 with the process GCIB 128A. Thecontrol system 190 monitors measurements of the GCIB current collectedby the substrate 252 in order to compute the accumulated dose receivedby the substrate 252. When the dose received by the substrate 252reaches a pre-determined dose, the control system 190 closes the beamgate 148 and processing of the substrate 252 is complete. Based uponmeasurements of the GCIB dose received for a given area of the substrate252, the control system 190 can adjust the scan velocity in order toachieve an appropriate beam dwell time to treat different regions of thesubstrate 252.

Alternatively, the process GCIB 128A may be scanned at a constantvelocity in a fixed pattern across the surface of the substrate 252;however, the GCIB intensity is modulated (may be referred to as Z-axismodulation) to deliver an intentionally non-uniform dose to the sample.The GCIB intensity may be modulated in the GCIB processing system 200 byany of a variety of methods, including varying the gas flow from a GCIBsource supply; modulating the ionizer 122 by either varying a filamentvoltage V_(F) or varying an anode voltage V_(A); modulating the lensfocus by varying lens voltages V_(L1) and/or V_(L2); or mechanicallyblocking a portion of the GCIB with a variable beam block, adjustableshutter, or variable aperture. The modulating variations may becontinuous analog variations or may be time modulated switching orgating.

The processing chamber 108 may further include an in-situ metrologysystem. For example, the in-situ metrology system may include an opticaldiagnostic system having an optical transmitter 280 and optical receiver282 configured to illuminate substrate 252 with an incident opticalsignal 284 and to receive a scattered optical signal 288 from substrate252, respectively. The optical diagnostic system comprises opticalwindows to permit the passage of the incident optical signal 284 and thescattered optical signal 288 into and out of the processing chamber 108.Furthermore, the optical transmitter 280 and the optical receiver 282may comprise transmitting and receiving optics, respectively. Theoptical transmitter 280 receives, and is responsive to, controllingelectrical signals from the control system 190. The optical receiver 282returns measurement signals to the control system 190.

The in-situ metrology system may comprise any instrument configured tomonitor the progress of the GCIB processing. According to oneembodiment, the in-situ metrology system may constitute an opticalscatterometry system. The scatterometry system may include ascatterometer, incorporating beam profile ellipsometry (ellipsometer)and beam profile reflectometry (reflectometer), commercially availablefrom Therma-Wave, Inc. (1250 Reliance Way, Fremont, Calif. 94539) orNanometrics, Inc. (1550 Buckeye Drive, Milpitas, Calif. 95035).

For instance, the in-situ metrology system may include an integratedOptical Digital Profilometry (iODP) scatterometry module configured tomeasure process performance data resulting from the execution of atreatment process in the GCIB processing system 200. The metrologysystem may, for example, measure or monitor metrology data resultingfrom the treatment process. The metrology data can, for example, beutilized to determine process performance data that characterizes thetreatment process, such as a process rate, a relative process rate, afeature profile angle, a critical dimension, a feature thickness ordepth, a feature shape, etc. For example, in a process for directionallydepositing material on a substrate, process performance data can includea critical dimension (CD), such as a top, middle or bottom CD in afeature (i.e., via, line, etc.), a feature depth, a material thickness,a sidewall angle, a sidewall shape, a deposition rate, a relativedeposition rate, a spatial distribution of any parameter thereof, aparameter to characterize the uniformity of any spatial distributionthereof, etc. Operating the X-Y positioning table 253 via controlsignals from control system 190, the in-situ metrology system can mapone or more characteristics of the substrate 252.

Control system 190 comprises a microprocessor, memory, and a digital I/Oport capable of generating control voltages sufficient to communicateand activate inputs to GCIB processing system 100 (or 200) a as well asmonitor outputs from GCIB processing system 100 (or 200). Moreover,control system 190 can be coupled to and can exchange information withvacuum pumping systems 170A, 170B, and 170C, first gas source 111,second gas source 112, first gas control valve 113A, second gas controlvalve 113B, beam electronics 130, beam filter 146, beam gate 148, theX-scan actuator 160, the Y-scan actuator 162, and beam current sensor180. For example, a program stored in the memory can be utilized toactivate the inputs to the aforementioned components of GCIB processingsystem 100 according to a process recipe in order to perform a GCIBprocess on substrate 152.

However, the control system 190 may be implemented as a general purposecomputer system that performs a portion or all of the microprocessorbased processing steps of the invention in response to a processorexecuting one or more sequences of one or more instructions contained ina memory. Such instructions may be read into the controller memory fromanother computer readable medium, such as a hard disk or a removablemedia drive. One or more processors in a multi-processing arrangementmay also be employed as the controller microprocessor to execute thesequences of instructions contained in main memory. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions. Thus, embodiments are notlimited to any specific combination of hardware circuitry and software.

The control system 190 can be used to configure any number of processingelements, as described above, and the control system 190 can collect,provide, process, store, and display data from processing elements. Thecontrol system 190 can include a number of applications, as well as anumber of controllers, for controlling one or more of the processingelements. For example, control system 190 can include a graphic userinterface (GUI) component (not shown) that can provide interfaces thatenable a user to monitor and/or control one or more processing elements.

Control system 190 can be locally located relative to the GCIBprocessing system 100 (or 200), or it can be remotely located relativeto the GCIB processing system 100 (or 200). For example, control system190 can exchange data with GCIB processing system 100 using a directconnection, an intranet, and/or the internet. Control system 190 can becoupled to an intranet at, for example, a customer site (i.e., a devicemaker, etc.), or it can be coupled to an intranet at, for example, avendor site (i.e., an equipment manufacturer). Alternatively oradditionally, control system 190 can be coupled to the internet.Furthermore, another computer (i.e., controller, server, etc.) canaccess control system 190 to exchange data via a direct connection, anintranet, and/or the internet.

Substrate 152 (or 252) can be affixed to the substrate holder 150 (orsubstrate holder 250) via a clamping system (not shown), such as amechanical clamping system or an electrical clamping system (e.g., anelectrostatic clamping system). Furthermore, substrate holder 150 (or250) can include a heating system (not shown) or a cooling system (notshown) that is configured to adjust and/or control the temperature ofsubstrate holder 150 (or 250) and substrate 152 (or 252).

Vacuum pumping systems 170A, 170B, and 170C can include turbo-molecularvacuum pumps (TMP) capable of pumping speeds up to about 5000 liters persecond (and greater) and a gate valve for throttling the chamberpressure. In conventional vacuum processing devices, a 1000 to 3000liter per second TMP can be employed. TMPs are useful for low pressureprocessing, typically less than about 50 mTorr. Furthermore, a devicefor monitoring chamber pressure (not shown) can be coupled to the vacuumvessel 102 or any of the three vacuum chambers 104, 106, 108. Thepressure-measuring device can be, for example, a capacitance manometeror ionization gauge.

Referring now to FIG. 7, a section 300 of a gas cluster ionizer (122,FIGS. 5 and 6) for ionizing a gas cluster jet (gas cluster beam 118,FIGS. 5 and 6) is shown. The section 300 is normal to the axis of GCIB128. For typical gas cluster sizes (2000 to 15000 atoms), clustersleaving the skimmer aperture (120, FIGS. 5 and 6) and entering anionizer (122, FIGS. 5 and 6) will travel with a kinetic energy of about130 to 1000 electron volts (eV). At these low energies, any departurefrom space charge neutrality within the ionizer 122 will result in arapid dispersion of the jet with a significant loss of beam current.FIG. 7 illustrates a self-neutralizing ionizer. As with other ionizers,gas clusters are ionized by electron impact. In this design,thermo-electrons (seven examples indicated by 310) are emitted frommultiple linear thermionic filaments 302 a, 302 b, and 302 c (typicallytungsten) and are extracted and focused by the action of suitableelectric fields provided by electron-repeller electrodes 306 a, 306 b,and 306 c and beam-forming electrodes 304 a, 304 b, and 304 c.Thermo-electrons 310 pass through the gas cluster jet and the jet axisand then strike the opposite beam-forming electrode 304 b to produce lowenergy secondary electrons (312, 314, and 316 indicated for examples).

Though (for simplicity) not shown, linear thermionic filaments 302 b and302 c also produce thermo-electrons that subsequently produce low energysecondary electrons. All the secondary electrons help ensure that theionized cluster jet remains space charge neutral by providing low energyelectrons that can be attracted into the positively ionized gas clusterjet as required to maintain space charge neutrality. Beam-formingelectrodes 304 a, 304 b, and 304 c are biased positively with respect tolinear thermionic filaments 302 a, 302 b, and 302 c andelectron-repeller electrodes 306 a, 306 b, and 306 c are negativelybiased with respect to linear thermionic filaments 302 a, 302 b, and 302c. Insulators 308 a, 308 b, 308 c, 308 d, 308 e, and 308 f electricallyinsulate and support electrodes 304 a, 304 b, 304 c, 306 a, 306 b, and306 c. For example, this self-neutralizing ionizer is effective andachieves over 1000 micro Amps argon GCIBs.

Alternatively, ionizers may use electron extraction from plasma toionize clusters. The geometry of these ionizers is quite different fromthe three filament ionizer described here but the principles ofoperation and the ionizer control are very similar.

Referring to FIG. 8, a method of forming shallow trench isolation on asubstrate using a GCIB is illustrated according to an embodiment. Themethod comprises a flow chart 800 beginning in 810 with generating aGCIB in a GCIB processing system. As described above, a pressurized gasis expanded into a reduced pressure environment to form gas clusters,the gas clusters are ionized, the ionized gas clusters are acceleratedand optionally filtered.

The GCIB may be formed and accelerated by an acceleration potentialranging from about 1 kV to about 70 kV. Alternatively, the accelerationpotential may range from about 1 kV to about 20 kV. In one embodiment,the acceleration potential is selected based upon the desired depth forthe dielectric layer. Alternatively, or in addition, the selection ofthe acceleration potential may be made based upon the type of layer(s)adjacent the dielectric layer.

The GCIB processing system can be any of the GCIB processing systems(100 or 200) described above in FIG. 5 or 6, or any combination thereof.A substrate can be positioned on a substrate holder in the GCIBprocessing system and may be securely held by the substrate holder. Thetemperature of the substrate may or may not be controlled. For example,the substrate may be heated or cooled during a growth process. Theenvironment surrounding the substrate is maintained at a reducedpressure, while the GCIB is formed from a pressurized gas mixturecomprising one or more film forming species.

The substrate can include a conductive material, a non-conductivematerial, or a semi-conductive material, or a combination of two or morematerials thereof. Additionally, the substrate may include one or morematerial structures formed thereon, or the substrate may be a blanketsubstrate free of material structures.

In 820, the substrate is irradiated with the GCIB to form an STIstructure by growing a dielectric layer in at least one region on thesubstrate. The GCIB is used to grow the dielectric layer in at least oneregion on the substrate to a pre-determined depth. When the substrate,or the irradiated layer or layers on the substrate, comprises silicon,SiO₂ may be grown via the GCIB by using an oxygen-containing gas, suchas O₂.

Although only certain embodiments of this invention have been describedin detail above, those skilled in the art will readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of this invention.Accordingly, all such modifications are intended to be included withinthe scope of this invention.

1. A method of forming a shallow trench isolation (STI) structure on asubstrate, comprising: forming a trench on said substrate; growing adielectric liner on at least one surface within said trench byperforming the following: generating a gas cluster ion beam (GCIB),selecting a beam acceleration potential and a beam dose to achieve athickness of said dielectric liner and to achieve a surface roughness ofan exposed surface of said dielectric liner less than approximately 20angstroms, and irradiating said trench with said GCIB to grow saiddielectric liner on said at least one surface within said trench; andthereafter, filling said trench at least partially with additionaldielectric material to form said STI structure.
 2. The method of claim1, wherein said growing said dielectric liner comprises oxidizing saidat least one surface within said trench to form an oxide layer, ornitriding said at least one surface within said trench to form a nitridelayer, or both oxidizing and nitriding said at least one surface withinsaid trench to form an oxynitride layer.
 3. The method of claim 2,wherein said GCIB comprises one or more gases selected from the groupconsisting of O₂, N₂, N₂O, NO₂, and NO, and an optional inert gas. 4.The method of claim 2, wherein said oxide layer comprises SiO₂, or saidnitride layer comprises SiN_(x), or said oxynitride layer comprisesSiO_(x)N_(y).
 5. The method of claim 1, wherein irradiating said trenchwith said GCIB forms said dielectric liner on a bottom surface of saidtrench while substantially avoiding growth of said dielectric liner onsidewalls of said trench.
 6. The method of claim 5, wherein saidirradiating said trench comprises oxidizing said bottom surface of saidtrench.
 7. The method of claim 1, further comprising: planarizing saidadditional dielectric material.
 8. The method of claim 1, furthercomprising: treating said additional dielectric material to correct aseam formed in said additional dielectric material.
 9. The method ofclaim 1, further comprising: annealing said dielectric liner.
 10. Themethod of claim 1, further comprising: generating another GCIB; andirradiating said dielectric liner with said another GCIB to introduceone or more species into said dielectric liner to a pre-determineddepth.
 11. The method of claim 10, wherein said introducing said one ormore species comprises introducing O₂, N₂, Xe, Ar, Si, BF₂, or Ge, orany combination of two or more thereof.
 12. The method of claim 10,wherein said introducing said one or more species comprises introducingO, N, C, H, S, Si, Ge, F, Cl, Br, He, Ne, Xe, Ar, B, P, or As, or anycombination of two or more thereof.
 13. The method of claim 10, furthercomprising: annealing said dielectric liner with said one or morespecies following said irradiating with said another GCIB.
 14. Themethod of claim 1, further comprising: using said STI structure in amemory device.
 15. The method of claim 1, further comprising: modifyinga beam energy distribution of said GCIB to achieve said surfaceroughness.
 16. The method of claim 15, wherein said modifying achieves asurface roughness less than 8 angstroms.
 17. A method of forming ashallow trench isolation (STI) structure on a substrate, comprising:forming a trench on said substrate; growing a dielectric liner on abottom surface within said trench by performing the following:generating a gas cluster ion beam (GCIB), adjusting a directionality ofsaid GCIB, and irradiating said trench with said GCIB to directionallygrow said dielectric liner on said bottom surface within said trenchwhile substantially avoiding growth of said dielectric liner onsidewalls of said trench; and thereafter, filling said trench at leastpartially with additional dielectric material to form said STIstructure.
 18. The method of claim 17, further comprising: modifying abeam energy distribution of said GCIB to achieve a surface roughness ofan exposed surface of said dielectric liner less than approximately 20angstroms.
 19. The method of claim 18, wherein said growing saiddielectric liner comprises oxidizing said bottom surface to form anoxide layer, or nitriding said bottom surface to form a nitride layer,or both oxidizing and nitriding said bottom surface to form anoxynitride layer.